Predicative nominals over subjects are also called predicate nominatives, a term borrowed from Latin grammars and indicating the morphological case that such expressions bear (in Latin).
These examples raise the following fundamental question: What characteristic of words and phrases allows or prohibits them from appearing as predicative expressions?
The friendly man found a large snake in his damp bag.
One can hence acknowledge a three-way distinction between predicative expressions, arguments, and adjuncts.
However, upon deeper examination, the lines between these categories become blurred and overlap can occur.
For instance, in the sentence Bill arrived drunk, one can judge drunk to be both a predicative expression (because it serves to assign a property to Bill) and an adjunct (because it appears optionally in the sentence).